Portable wireless devices, such as smart phones and tablets, have antennas incorporated into their industrial designs. These antennas can be multi-band, operating on multiple frequency bands such as in the range of 700 MHz to 2690 MHz. It is expected that many more frequency bands will be implemented in portable devices in order to ease the capacity congestion of the wireless cellular frequency bands. Impedance matching over a large range of Radio Frequency (RF) bandwidth becomes increasingly more challenging as the number of supported bands increases.
As a result, researchers in the field of cellular wireless technology have focused on what has become known as “tunable systems”, i.e., the means of tuning and matching between RF components themselves and their associated antenna systems. The impedance transformation and matching problem has been known in the industry since the early days of wireless technology, viz., that a source of RF energy should match the impedance of its respective load in order for that source to deliver maximum useful power to the load.